Fargo Kid (1940)

The Fargo Kid (Tim Holt) rides into Micaville (a favorite town name in RKO westerns) on a sorrel horse he won in a draw on the road with gunman Deuce Mallory. The horse identifies him to crooks Nick Kane and Bush Cleveland as killer-for-hire Mallory, and they promptly pay him $5000 to kill prospector Caleb Winters.